Precipitation chances will return to the Palmetto State overnight into Monday as high pressure moves offshore and a cold front approaches from the west.
A ridge of high pressure Sunday was tracking eastward into the Atlantic allowing for a shift in winds from easterly to southerly. Moisture is forecast to surge into the state beginning Sunday night ahead of a low pressure system and associated cold front, which will continue eastward away from Plains. This influx of moisture will result in an increase in precipitation chances from around midnight through sunrise Monday across portions of the UpState as the cold front approaches South Carolina.
There will be a concern for a brief period of wintery precipitation late Sunday and overnight into Monday morning as temperatures dip into the mid 30s. Northern UpState areas and locations at higher elevations could experience temperatures at freezing for a brief period of time which will increase wintery precipitation chances. Accumulations are anticipated to be sparse before the wintery mix turns to rain by Monday morning.
Scattered showers will continue eastward into the Midlands with chances increasing in the afternoon. Although upper level wind shear will be moderate to strong ahead of the cold front the severe threat will be minimal throughout the event. Atmospheric instability remains restricted across the Palmetto State which will quench widespread thunderstorm development. The highest rainfall amounts should favor east towards the Atlantic coast as showers become more widespread during the mid to late afternoon and continuing into the evening before tapering off behind the passage of the cold front.
Warm advection preceding the cold front will allow afternoon temperatures to climb to above-average closest to the coastlines. Highs are expected to be in the upper 60s to lower 70s across Pee Dee and the Lowcountry. Near-seasonal highs in the mid-60s are forecast in the Midlands. Finally, Upstate regions, which will experience the passage of the cold front early Monday, will only rise into the low to mid-50s by the afternoon, which is slightly below average.
A few lingering showers are possible overnight into Tuesday with conditions gradually clearing from west to east. The cold front is forecast to be offshore by early Tuesday morning with high pressure building in from the west. A brief cool-down is expected Tuesday as a dry and northerly wind penetrates the state around the high pressure system. Temperatures will warm back up by Wednesday as the high pressure moves offshore, delivering a warmer, easterly flow. Mostly dry and mild conditions are forecast through at least Thursday before another frontal boundary approaches from the west.